January 13, 2020

Via Electronic Mail (rule-comments @scc.gov)

Ms. Vanessa Countryman
Secretary
U.S. Securities and Exchange Commission
100 F Street NE., Washington, DC 20549

Re: File Nos. SR-BOX -2019-19 mu/ SR-BOX-2019-37

Dear Ms. Countryman:

The Securities Industry and Financial Markets Association (“SIFMA”}1 appreciates the opportunity to comment on the above-referenced filings (the “Filings” or the ” BOX Filings”) made by BOX Exchange LLC (” BOX” or ” Exchange” ) with the Securities and Exchange Commission (“Commission”) and respectfully requests more time to provide feedback on the Filings. In the Filings, SR-BOX-2019-19 and SR-BOX- 2019- 3 7, BOX seeks approval to Adopt Rules Governing the Trading of Equity Securities on the Exchange Through a Facility of the Exchange Known as the Boston Security Token Exchange LLC (“BSTX”) and a Proposed Rule Change in Connection With the Proposed Commencement of Operations of Boston Security Token Exchange LLC as a Facility of the Exchange, respectively. 2

BOX has proposed two separate filings with the Commission, which collectively, would allow the Exchange to commence operations of BSTX. BSTX  would be a facility of the Exchange that will operate a market for the trading of digital security tokens. BSTX would operate a fully automated, price /time priority execution system for the trading of ” security token s,” which would be equity securities that meet BSTX listing standard s and for which ancillary records of ownership would be able to be created and maintained using distributed ledger (or ” blockchain” ) technology. The security tokens would qualify as ” NMS Stocks” pursuant to Regulation NMS. All transactions in security tokens would clear and settle in accordance with the rules, policies, and procedures of registered clearing agencies.